Flashcards in Preterm labour Deck (49):
What is term?
Period between 37-42 completed weeks of gestation
What is post term?
Strictly period after 42 weeks gestation
Period between 23-36 completed weeks of gestation
What is human preterm labour generally defined as?
Presence of uterine contractions and progressive cervical effacement and dilation occurring between 23-36 completed weeks of gestation
What is important to consider as well as gestation length in preterm labour?
Birthweight; often increases parallel with gestation length but pathological situations may change relationship.
What is the normal birthweight for a term infant?
2500 - 4000g; mean 3250g
Why is estimated date of confinement essential?
To allow reliable subsequent determination of normality of gestation length and birthweight
What are the conditions which may contribute to preterm labour? (have etiological association)
-Previous preterm birth
-APH (esp abruption)
- cervical insufficiency
-Infection: genital tract or abdominopelvic structures; systemic (flu)
-Uterine abnormality: congenital, fibroids
-Placental insufficiency: PET, maternal disease (renal, autoimmune, thombophilia)
When does uterine over distension occur?
Polyhydramnios and multiple gestations
What are the pathogens which commonly infect the genital tract and trigger preterm labour?
What uterine abnormalities may precipitate pre term labour?
-incomplete Mullerian duplications (e.g. subseptate uterus)
What are the environmental / social causes of pre term labour?
-Tobacco / smoking
-Illicit drugs (coke, crack)
-Sexual activity (weak)
-Exercise (weak if reasonable exercise)
Presentation preterm labour?
-Increase in uterine contractions
-Sudden loss of clear fluid (i.e. membrane rupture)
-Sudden increase in vaginal discharge
How is preterm labour diagnosed?
-Hx: contraction details, EDD
-PEx: sterile spec, exclude ROM, progressive cervical effacement and dilation
-Ix: foetal fibronectin, amnisure
Why is a sterile speculum exam conducted in suspected preterm labour?
-Check for cervical changes
-Check for ruptured membranes
-Exclude cord prolapse
-allow micro swab of cervix, amnisure if required
-abdo palpation of uterus for contractions
Initial management of preterm labour?
-Aetiology and Rx if appropriate
-Admit to perinatal centre with appropriate facilities; neonatal team aware
-Observe (hours) and assess for cervical change
-Foetal fibronectin swab
-Consider: CST and MgSO4, GBS prophylaxis
What is foetal fibronectin?
Choriodecidual glycoprotein released into the vagina at a preclinical stage of preterm labour
What must be decided once preterm labour diagnosed?
Advisability of tocolytic therapy
Contraindications to IV salbutamol in preterm labour tocolysis?
-Diabetes (causes hyperglycemia)
-maternal cardiac disease (tacky)
-APH (subverts normal CV homestatic mechanisms)
-ROM (age dependent; risk of chorioamnionitis outweigh benefit)
-Cervical dilation >4cm
-Genital tract infection
-FDIU or abnormality incompatible with life
Why is tocolysis contraindicated with cervical dilation >4cm?
Tocolysis ineffective by that stage
What is the current drug of choice as a tocolytic?
Why can't IV salbutamol and PO nifedipine be given together?
CV side effects: hypotension, tachycardia, palpitations
What are the options for tocolysis?
-Indomethacin (PG synthesis inhibitor)
-Atosiban (oxytocin receptor antagonist)
What is the main utility of tocolysis given their disappointing effect on perinatal outcomes?
-1) Maintaining uterine quiescence during transfer of a patient in preterm labour
-2) Maintaining foetus in utero for 24-48h to allow medications for foetal lung development
How may the incidence of neonatal respiratory distress be dramatically reduced?
Corticosteroids given maternally 24-48h prior to delivery between 26-32 weeks gestation
Why are corticosteroids effective in reducing neonatal respiratory distress?
Cross placenta and trigger production of lung surfactant in the foetus
What other conditions are improved by the maternal administration of corticosteroids?
How is incidence of CP reduced?
Magnesium sulphate administered IV to mother at risk of early preterm
Foetal factors to consider in mode of delivery in preterm labour?
Why do premature foetuses presenting breech usually require C section?
Increased risk of hypoxia due to cord prolapse and/or cervical entrapment of foetal head in an incompletely dilated cervix
When do membranes usually rupture?
Rupture during labour at end of first stage or beginning of second
Why is PROM managed differently depending on gestational age?
If less than 34 weeks, risks of prematurity outweigh risk of intrauterine sepsis (so manage conservatively).
Deliver after 34w as intrauterine sepsis greater risk than prematurity
What are the risks of PROM?
-Umbilical cord prolapse
When is umbilical cord prolapse likely to occur?
-Foetal presenting part not engaged in pelvix or fits poorly into LUS and against cervix (e.g. foot)
What is the most suggestive sign of PROM?
Pool of clear fluid in the posterior fornix (can analyse for alkaline pH, amniotic fluid factors, phospholipids)
How may membrane rupture be distinguished from urinary incontinence?
Give mother perineum: colours urine orange
What must be done if conservative management of PROM is undertaken?
-cervical and urine micro
-maternal temp and pulse
-observation of continuing liquor loss for clarity v purulence
-appearnce of uterine tenderness
How is PROM diagnosed?
-Hx: gush of fluid, persistent leak
-PEx: obvious liquor, cough test, pooling on spec exam
-Take a HVS and LVS as time of examination + CRP, FBE, MSU
What is the corticosteroid of choice in preterm foetus?
Betamethasone 11.4mg IM; 2 doses 24h apart
Management if contractions of preterm labour settle?
-Exclude treatable precipitants
-Monitor closely for further episodes
-If no signs of preterm labour, do not give ABx or MgSO4
Neuroprotection mx strategy in preterm labour?
-4g loading dose over 15min for imminent delivery.
-non imminent: 4g loading dose, 2g/h maintenance
What does MgSO4 do for foetus?
Foetal neuroprotection: reduces the risk of CP and gross motor dysfunction when given to women at risk of PTB.
Describe management of preterm labour and birth
-Paeds, anaesthetics, theatre available
-IV access, FBE, G and H
-MgSO4 loaded 4g/15m
-Syntocinon infusion on standby (40IU in 1000mL and 10U in 1000mL)
-Active management third stage (40U syntocinon)
- Placenta for histopath
What are the short term problems in the neonate of preterm birth?
-Resp: RDS, bronchopulmonary dysplasia, apnoea of prematurity
-CV: PDA, hTN
-Retinopathy of prematurity
What are the long term complications of preterm birth?
-Neurodevelopmental disabilities: (motor eg. CP, sensory impairment, cognitive impairment, behaviour / psych)
-Chronic medical (growth, GIT)
-Adult health conditions (insulin resistance, hypertension, reduced fertility)
Which women should receive MgSO4?
Women less than 32w with delivery imminent within 24h
Ix in preterm labour?
- Urine culture
- Drug testing if RFx (cocaine and abruption)
- Foetal fibronectin if less than 34w and cervial dilation less than 3cm
Mx of women 34/40+ presenting in preterm labour?
Admit for delivery.
- NO CST/ Mg etc
- Observe 4-6h
- Exclude complications (abruption, chorioamnionitis, PROM)
- If settles can discharge with follow up